Lapping process



March 23, 1943. D. A. WALLACE 2,314,533

VLAPPING PROCESS Filed July 17, 1941 27 u INVENTOR (Tm-i fiarz'J 1 7. h allace.

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ATTORNEYS.

Patented Mar. 23, 1943 LAPPING PROCESS I David A. W'a1lace, D,et1-oit,- Micht, assignor .to

Chrysler Corporation, Highland Park, Mich., a 1 corporation of Delaware I 1 Application July 17, 1941, scr'ie1No. 402,734. Y 6 Claims. (01. 51 29o) .1 FUNIYTED P STATES PATENT I O F E? My "present invention relates to afmethod and means for manufacturing a tubular shaft having its bore coaxial with its outer surface within unusually closetolerances. rThe present invento shafts which do not require such-shoulders i I, in which case a piece of bar stock of substan-" tially the desired diameter may beprovided with a groove or grooves adjacent an end, which por tlon is of utility in manufacturing torque transtion nfay be cutofi efter he f n fin shing opermitting shafts,- especially where 'ghtness is of ation; The purpose of the shoulders this to importance-as'in airplanes. providea; groove l3 by means of which the blank The object of the present invention is'to promay be fedlongitudinall n-as will presentlyapvide'a shaft having a bore which is concentric pear. The" blank is now bored longitudinally to withthe axis of the shaft and concentric with pr v e n r b r having its surface as its outersurface within limits heretofore impos .ne arly concentric to the longitudinal axis of the sible to obtain. This object'is achieved in part blank as modern machinery can make i i; theby providing a blank with an accurately finished surfaceof the bore "be n t e ned-0r otherbore, forming the outer surface of the shaft Wise finished to the desired dimension. The roughly concentric with the bore and slightly blank is now preferably heattreated or otherlarger than'the desired dimension, then mount- WISBDTOCESSBCI t0 pe ma fi thereof ing the shaft' up'ona mandrel having a true surthe characteristics desired of theflnished article. face and a diameter'slightly smallerthan thevT e Oute su c 0 e blank 5 P evidiameter of the here so, as to provide a space ously' stated, .of .a diameter in excess of that between the surfaces of the mandrl'and of the '20 desired- In Order t mo this e cess material. bore between which on or other fluid under high the blank is finished in the apparatus of my pressures may be forced was to form a cylinder inventi n. This appar us comprises s nt a y, of fluid under pressure floatingly supporting the a mandrel I5 having an accurately finished surblank with the axis of the'bore accurately coin- 7 face and adiameter slightly lesser than the illciding with the axis of-fthe mandrel. Thereafter emeter of the bore M. The mandrel'is pr ferthe outer surface of the blank is finished-to size b yxin excess of twice the len th ortheshaft by surface finishing toolsoperating upon the t on, n Provided With a longitudinally. blank while'the blank revolves about and reciproten n ie h v ng n outlet 11 to the cates along thermandreln surface of the mandrel at the central portion The objects and advantages of the present er e an el. with the blank mounted invention will be more readily understood by th on, isnow mounted in the-finishin m reference to the following specification and draw Chine, pr a y up n the centers; 18 adapted ing wherein like numerals refer to like part to hold the mandrel firmlyin-positlon; The finthroughout, 7 ishing machine is preferably provided with a In the drawing, 5 clamp l9 by means of which the mandrel is pre- Fig. 1 discloses a piece of round bar stock from nte from rotating. The lon itu inal bore l6 which the shaft isto be manufactured; in the mandrel is connected to a tube 20 by Fig."2 discloses the blank which is manufacmeans'of which oil or other fluidunder pressure t d f th d b t k; 7 )may be forced into the space between' the sur- Fig. 3 discloses the mechanism'formin part 01 40 face of the mandrel l5 and the surface of the my invention with the blank in position thereon; bore e fl r p ss s u ifo ly and, in alldirections surrounding the opening I! so Fig. 4 is a'sectional view taken'substantially as to form a cylindrical cushion fioating y supalong'nne 4+4 of Fig 3, r porting the blank upon the mandrel with the practicing my i ti n a piece of d surface of the bore l4 concentric with the surbar stock I0 is milled to provide spaced shoulface of the mandrel l I ders ll adjacent an end' hd a shait'portion I: The blank sadabt d t be p at d l nsi having a rough finished diameter larger than tudinally of the mandrel 15 by means of a travelthe desired diameter. The particular shaft 11118 fork ounted upon a worm shaft 23; the herein disclosed is adapted to be associated withtines" 0 e f fit ng-into the roove ll be connecting mechanism partly through the. me tween the shoulders ll. Obviously, if the groove dium of the shoulders ll so that the bar stock I3 is sunk below the surface of the shaft II, the i0 is provided with sufliciently large diameter to k 22 m y een d toengaze s ch a groove. provide the shoulders integrally with the shaft The eng h of the Worm shaft 23 is-such as to 12''. However, the present invention "is applicable traverse the surface of the shaft'to be finished .the worm shaft 23.

past surface finishing means provided adjacent the central portion of the mandrel I5 near the outlet H. R

The work is preferably accomplished by means of a driven grinding wheel 25 revolving at high speed, past which the surface is reciprocated by As the grinding wheel operates upon the surface, the blank itself is caused to revolve at. a surface'speed tending to approach the surface speed of the wheel so that a highly polished surface is imparted to the blank. A pressure wheel 26 may be provided to eliminate any tendency to vibrate. The pressure wheel 26 may be of such character as merely to press against the material or composed of surface removing substance. The

may in itself be pressure wheel is preferably mounted upon a swinging arm 21 and urged toward the work by a light spring 28.

In practicing my invention the outer diameter of the blank is formed to a rough finishof approximately .01 of an 1-inch larger .than the de-- sired final size before forming the bore and heat treating the blank. The mandrel I5 is preferably provided with a truesuriace approximately .001 of an inchsmaller in diameterthan the diameterof the,bore H. The fluid provided for fioatingly supporting the blank upon the mandrel is preferably oil and is preferably forced through the bore 16' under pressures of at least 25 pounds tip-the square inch and upward to as high as .500 pounds to the square inch. The surface finishing operation 'is preferably that type of operation characterized by lightly engaging an abrasive wheel of medium grain dimensions against the surface of the work so astoremove the surface inequalities above the base metal. when the extra.01"inch outer dimension is'removed by the finishing operation the surface will have only few: irregularities thereinandjsuch as exist will extend belowthe base surface. By means of this Inthod apparatus tubular shafts should'be provided having. uniform concentricity from end to end; and wall thickness dimensions held closer than .OOlcf an inch.

Havingdesc'ribed and illustratedthe preferred embodiment of my invention, it should be apparent'tothose skilled in the art that numerous types of shafts may be formed: thereby, and that numerous modification's' in arrangement and detail of the mechanism may be'provided within the scope of my invention. It should also be apparent to'those skilled in the art that numerous variationsin the steps to whichthe blank may be subjected before reaching final form may 00- our, and that, nevertheless the process herein described and claimed in the following claims would not be affected by any treatment imparted to'the blank prior to' application of my process or subsequent thereto. i V I claim as my invention thefollowing method and apparatusz V t t 1. The process of forming a tubular shaft having its borecoaxial with its outer surface comprisingthe steps of forming a tubular blank having its greater diameter slightly larger than desired and its bore finished to close tolerances,

supporting the blank: on a cylindricalmandrel having a. diameter slightly smaller than the diameter of said bore, revolving the blank relativeto said mandreL'finishing'the outer surface of the-blank to size by applying a finishing tool against said outer surface mainly from one direc; tion substantially radially of said blank during revolvingof the latter and forcing fluid under 2. The process of forming a tubular shaft having its bore coaxial with its outer surface comprising the steps of forming a tubular blank having its greater diameter slightly larger than desired and its bore finished to close tolerances,

supporting the blank on a cylindrical mandrel having a diameter slightly smaller than the diameter of said bore. and a length in excess of twice the length'of the shaft surface to be finished, revolving the blank relative to said mandrel, reciprocating the revolving blank past surface finishing means applied against said blank mainly in one direction radially thereof to finish the outer surface of the blank to size and forcing fluid under pressure into the space-between the surfaces of said bore and said mandrel during said rotation and finishing whereby to provide a substantially cylindrical cushion of fiuid under pressure fioatingly supporting the blank with said bore substantially coaxially located with respect to said mandrel. v, t a e V -3. The process of forming a tubular shaft having its bore coaxial'with its 'outer surface comprising the steps of forming a .tubular blankhaving its greater diameterslightly larger than desired and its bore finished to close tolerances, supporting the blank on a cylindrical mandrel having a diameter slightly smaller than the diameter of said bore, revolving the blank relative to said mandrel, bringing suceessivelongitudinal increments of the revolving blank into contact with a travelling grinding surface applied against said blank mainlyin one direction radially thereof and held at a fixed distance from the axis of said mandrel and forcing fiuid under pressure into the space between the surfaces of said bore and said mandrel during said revolving and grinding operations whereby to provide, a substantially cylindrical cushionof fluid under pressure fioatingly. supporting the blank with said bore substantiallycoaxially located with respect to said mandrel. v 1

4. The process of forming a tubular shaft having its-bore coaxial with its outer surface comprising the steps of forming a tubular blank having its greater diameterslightly. larger than desired and its bore finished to close tolerances, supporting the blank on a. cylindrical mandrel having a diameter slightly smaller than the diameter of said bore, revolving the blank relative to said mandrel, passing the blank longitudinally between a revolving grinding wheel and a pressure wheel whose axes lie in substantially the same plane with, andparallel to, the axis of. said mandrel and forcing fluid under pressure into thespace between the surfaces of said bore and said mandrel during said revolving and grinding operations whereby to provide a substantially cylindrical cushion of fluid under pressure fioatingly supporting the blank with said bore substantially 'coaxially located with respect to said mandrel,

;5.. The process of forminga tubular shaft having its bore coaxial with its outer surface comprising the steps of forming a tubular blank havingits. greater diameter, slightly larger than desired and its bore finished to close tolerances, supporting the blank on a cylindrical mandrel having a diameter slightly smaller than the diameter 01' said bore, revolving the blank relative to said mandrel, reciprocating the revolving blank longitudinally past the periphery of a revolving grinding wheel whose axis is substan-- tially parallel to the axis of saidmandrel and whose periphery is maintained at a distance from the axis of said mandrel equal to the desired outer radius of the finished shaft and forcing fluid under pressure into the space between the surfaces of said bore and said mandrel during said revolving and reciprocating operations whereby to provide a substantially cylindrical cushion of fluid under pressure floatingly supporting the blank with said bore substantially coaxially located with respect to said mandrel;

6. The process of forming a tubular shaft having its bore coaxial with its outer surface comprising the steps of forming a tubular blank having its greater diameter slightly larger than desired and its bore finished to close tolerances,

ting the blank to revolve due to the frictional drag of said grinding wheel while being reciprocated and forcing fluid under pressure into the space between the surfaces of said bore and said mandrel during said revolving and reciprocating operations whereby to provide a substantially cylindrical cushion of fluid under pressure float-- ingly supporting the blank with said bore sub-, stantiallycoaxially located with respect to said mandrel.

DAVID A. WALLACE. 

